Airless spray guns



Jan. 31, 1961 n.1. PEEPS 2,969,926

AIRLESS SPRAY yGUNS Filed Oct. 50, 1956 2 Sheets-Sheet 1 BY h 1 @g4 y 2MHTTOR N EYJ Jan. 31, 1961 D. J. PEEPs 2,959,926

AIRLESS SPRAY GUNS Filed oct. so, 195e 2 Sheets-Sheet 2 INVENTOR. Dana/0d Peeps BYQMAQQL United States Patent AIRLESS SPRAY GUNS Donald J.Peeps, Rossford, Ohio, assigner to The De Vilbiss Company, Toledo, Ohio,a corporation of Ohio Filed Oct. 30, 1956, Ser. No. 619,183

"4 Claims. (Cl. Z39- 526) This invention relates to spray guns lfor theairless Vapplication of viscous materials and is particularly directedto a contro-l valve mechanism for such a spray gun.

It has :heretofore been proposed to spray heated liquid materialswithout the use of an atornizing air stream, and theoreticallyatomization which takes place as a result of a sudden pressure releaseshould give a more uniform coating than one deposited with the aid ofentrained air. One of the diiculties with airless spray guns has beenthat the very high pressure on the liquid has made it difficult tooperate the material control valve. In many instances the valve hasopened and closed so slowly that a substantial portion of the streamfailed to disperse immediately after opening and immediately prior toclosing of the valve. This sluggish valve action has resulted innon-uniform and unacceptable coatings. p It has been proposed to providean auxiliary, air operated piston to open the valve of an airless spraygun, and it has also been proposed to provide a complex series of togglemechanisms foi the purpose of imparting a snap action to the rearward oropening excursion of the material control valve. Such attempts have beenunsatisfactory for various reasons and have not been widely adopted.

The present invention Ahas for its primary object to provide a materialvalve control mechanism for an airless spray gun in which pressuredifferentials in the heated liquid itself are utilized to impart a rapidand positive motion to the valve parts.

Another object of the invention is to provide a material valve controlmechanism in which undesired pressure differences are balanced out,leaving only those pressure differences which are required for theproper fast operation of the valve.

Other objects and advantages of the invention will become apparent fromthe following description of a preferred form thereof, reference beinghad to the accompanying drawings, in which- F-ig. 1 is a fragmentarycentral vertical sectional view of a spray gun embodying the presentinvention;

Pig. 2 is a front elevational view with parts in section; and

Fig. 3 is a fragmentary, somewhat enlarged and diagrammatic sectionalview showing the control valve of the present invention in an openposition.

Briey stated, the present invention comprises a spray gun for theairless discharge of liquid materials comprising a gun body having twoliquid chambers therein,

together with means to supply liquid under pressure to ice shown in anembodiment including a gun lbody 10 having a handle 12 dependingtherefrom, a trigger 14 being pivotally attached to the body by a pintle16 in the usual manner. A front body portion 18 is attached to the mainbody 10 by a bolt 20 extending longitudinally of the gun and the matingsurfaces of the body portions are insulated from each other by asuitable heat resisting washer 22 which is preferably of a plasticmaterial.

The front body portion 18 has a longitudinal discharge passage orchamber 26 which is threaded at its front end to receive a stationaryvalve seat member 28. The stationary member 28 has an opening or spraynozzle 30 in its front wall through which heated liquid may flow underhigh pressure to expand and atomize during operation. This opening 30 isclosed by a material control valve 32 which may be of any suitable form,a simple at faced surface type valve being shown in the drawings. Such avalve is advantageous because it gives a maximum valve opening with aminimum longitudinal excursion. The valve itself is preferably formed ofa heat resistant plastic material and is carried at the end of a valveoperating rod 34.

The rear end of the valve carrying rod 34 is attached as by a threadedconnection to a head 38 to which is welded or otherwise fixed alongitudinally resilient sealing member such as a bellows seal 40. Thebellows 40 contains air at atmospheric pressure in its interior sinceits outermost end, remote from the head 38, is fixed in position to sealthe end of bore 26. Since the head of the bellows 40 is exposed towhatever pressure exists in chamber 26, a valve opening force is exertedon the annulus defined by the area of the bellows head minus the area ofthe valve 32. This force is utilizedy as hereinafter described. A plug42 may be threaded into the gun body and used to seat the bellows wallagainst an adjacent surface of the body in a uid tight joint. Therearward movement of the rod 34 may be limited in any suitable manner asby a stop pin 43 inserted in the plug 42.

An adjusting rod 44 extends rearwardly inside the bellows 40 from thehead 38 and may, if desired, be made integral with the head. Ilheadjusting rod passes freely through the plug 42 and extendsinto a springretainer 46 carried in the main gun body 10. The bellows 40 acts as asubstantially frictionle'ss fluid tight packing around rod 44. Anadjusting spring 50 is disposed Within the retainer and is compressedbetween a head 52 on the rod 44 and a threaded cup 54 extendingoutwardly from the rear of the retainer into an exposed position where anut-like head thereof can be readily grasped by the operator to turn thecup 54 in or out and thus increase or decrease the force of spring 50against the adjusting rod 44.

The present invention is particularly directed to a novel means tocontrol the admission of fluid into chamber 26 in such a manner that anextremely rapid increase and decrease in pressure in that chamber isavailable for opening and closing valve 32. To this end, the front gunbody portion 18 is provided with a vertical iluid conduit 60 which maybe conveniently formed in an insert 62. threaded into the body. Theinsert 62 is ground dat on its lower face 64 to act as a valve seat fora resilientV annular valve 66. Valve 66 is carried by a holder 68 whichhas a spherically formed outer surface lying closely adjacent the wallsof the bore of the body which form the fluid passage. The sphericalportion of the valve holder is slotted at spaced points so that fluidcan ow easily from below the holder to the valve 66, yet the sphericalsurface can act as a rocking guide for the holder.

A stem 70 depends from the valve holder 68 and straddles an operatingrod 72. Rod 72 is connected on each side to a balancing bellows, theinteriors of which escasas are at substantially atmospheric pressure.The front bellows, designated 74 in the drawings, has its open or outerend held in place by a threaded plug 76 and is guided for reciprocationby a center stem 78 the end of which is inserted into a bore or recessin the plug. The rear bellows, designated 80 in the drawing, is'similarly held in place by a 'sealing plug 82 and encases a guiding andoperating rod 84 which is either integral with, or attached to a, therod 72. The operating rod extends through the rear plug 82 and isoperatively connected with the trigger 14. It will thus be seen that thebellows 74 and 80 constitute a substantially frictionless sealing meansfor the valve operating rod 72 and that the seal is balanced because theeiective area of the front or exposed portion of each bellows is thesame and is exposed to the same fluid pressure. y

Fluid enters the front gun body by a iirst chamber or lateral passage 86in open communication with the vertical passage 60, intersecting thesame at the bore which contains the sealing bellows. The passage 86extends on each side of the center of the gun and is in turn intersectedby vertical inlet and outlet passages 88 and 90 so that fluid may becirculated into and out of the gun in preparation for a sprayingoperation as hereinafter described. In some instances it is notnecessary to circulate heated fluid through the gun, as where a iluidheating hose is used, and .in these cases there will be required only asingle vertical passage opening directly into the iirst chamber formedby passage 66 and the volume surround ing the bellows 74 and 80. v

In operation, heated paint or other duid material is circulated throughthe gun until such time as the front gun body portion 18 is suicientlyheated that operation can commence withoutdanger of cooling the liquidto the point that 'sluggish or ','u'nsatisfacto'ry operation willresult. Liquid at a pressure of 250 'to9OQpoi1nds per square' vicl'i(depending an 'the material) is thus, present in the here 86 and exertsits pressure against the head of bellows 74 and 80. The operator iirstmoves the trigger 14 rearwardly thus pulling rod 72 rearwardly. It willbe seen that since both bellows 74k and 80 are attached to rod 72 thepressure of the liquid is balanced out and thus exerts no force, eitherforwardly or rearwardly, on rod 72.

Moving rod 72 rearwardly causes the depending valve stems 70 to rockthecontrol valve 66 Varound a'point on the rear of its circumference andcauses the valve to move away from its seat rst at the` front edge.Assoon as the valve 66 cracksV away from itsseat, liquid flows fromY theirst chamber in which it has been circulating and enters the passage 60and commences to buildv up a pressurek therein, which pressure tends toopen the control valve 66 more fully by increasing the pressure on theYtop thereof to a value nearly equal to the pressure on the lower face.The full pressure of the heated liquid thus appears quite rapidly in thesecond or discharge chamber 26 formed by the longitudinal bore of thegun and closed by the discharge valve 32. This pressure isexertedrearwardly in a direction tending to open the valve, on theannulus at the head of the bellows 40, above described. This pressure isresisted only by spring 50 so that valve 32 opens when the pressuretimes the area of annulus exceeds the force of the spring. As soon asvalve 32 opens slightly,

the full pressure in chamber 26 is exerted against the front.

face thereof andthe rearward force tending to moveV the valve to a fullyopened position and to hold it there is increased. l

Spraying thus proceeds with the liquid atomized by the release ofpressure beyond the orice 30. By reason of the fact that liquid isflowing rapidly around the circum ference of control valve 66 there isan area of reduced pressure above this valve due to the velocity of theliquid so that the operator must hold trigger 14 in valve openingposition.

When it is desired to close the discharge valve 32 the operator releasesthe trigger 14. The aforementioned pressure dilerence on control valve66 immediately causes the valve to move towards a closed position. Sincevalve 32 is still fully open the large pressure reduction caused bycontinued ilow of even a very small quantity of duid from chamber 26 issufcient to seat valve 66 very iirmly by reason of the pressuredifference above and below it. Further, since there is now no continuoussupply of liquid to chamber 26 the pressure therein drops to atmosphericpressure almost instantaneously and spring 50 can easily heat valve 32against the plate or stationary valve member 28 and close olf thedischarge orifice 30. i,

It will thus be seen that the discharge valve 32 is operated by pressurein chamber 26 and that this pressure is controlled by fluid flowing pastcontrol valve 66 which, in turn, is opened mechanically and is closed bya difference in pressure on its upper and lower faces.

While the invention has been shown in conjunction with a specific formand disposition of the parts it should be expressly understood that itis capable of numerous modifications and changes without departing fromthe scope of the appended claims.

What I claim is:

1. A spray gun for the airless spraying of liquid coating materials,said spray gun comprising a gun body having rst and second liquidchambers and a passage therebetween, means for supplying coating liquidunder pressure to said lirst chamber, a control valve associated withsaid passage to close and to open said passage to theilow of coatingliquid from said first chamber to said second chamber, ysaid controlvalve having a stem projecting into and located wholly within said firstchamber, a pressure-balanced, trigger-actuated mech-A anism carried bysaid Vbody and operatively connected to said stem and movablein adirection laterally of said Stein to move said sftem laterally and tocause lsaid valve t rock about a point on its periphery thereby lto opensaid valve, trigger means located outside said first chamber andassociated with vsaid spray gun body for manually operating saidmechanism, means forming a spray nozzle in communication with saidsecond chamber, a discharge valve between said second chamber and saidspray nozzle, means normally urging said discharge valve toward a closedposition, and means operatively connected to said discharge valve andresponsive to liquid pressurein said second chamber to open saiddischarge valve rapidlyV when pressure in said second chamber exceeds apredetermined value, whereby said coating liquid will be substantiallyinstantaneously sprayed from said spray nozzle when liquid pressure insaid second chamber builds up above said value when said control valveis opened to supply coating liquid under pressure from said rst chamberthrough said passage to said second chamber.

2. A spray gun for the airless spraying of liquid coating materials,said spray gun comprising a gun body having first and second liquidchambers and a passage therebetween, means for supplying coating liquidunder pressure to said rst chamber, a control valve associated with saidpassage to close and vto open said passage to the flow of coating liquidfrom said rst chamber to said second chamber, said control valve havinga stem projecting into and located within` said first chamber,triggeractuated mechanism carried by said body and operatively connectedat an intermediate portion topsaid stem andV movable in a directionlaterally of said stem to move said stem laterally and to cause saidvalve to rock about,

a point on its periphery thereby to open said valve, a pair of balancingbellows, the interior of which is subjected to atmospheric pressure,said bellowsencompassing said trigger-actuated mechanism withinsaidiirst chamber on each side ofv said intermediate portion to balance outthe effect of duid pressure in said first chamber on saidtrigger-actuated mechanism, trigger means located outr` side said r'stchamber and associated with said spray gun body for manually operatingsaid mechanism, means forming a spray nozzle in communication with saidsecond chamber, a discharge valve between said second chamber and saidspray nozzle, means normally urging said discharge valve toward a closedposition, and means operatively connected to said discharge valve andresponsive to liquid pressure in said second chamber to open saiddischarge valve rapidly when pressure in said second chamber exceeds apredetermined value, whereby said coating liquid will be substantiallyinstantaneo-usly sprayed from said spray nozzle when liquid pressure insaid second chamber builds up above said value when said control valveis opened to supply coating liquid under pressure from said iirstchamber through said passage to said second chamber.

3. A spray gun for the airless spraying of liquid coating materials,said spray gun comprising a gun body having first and second liquidchambers and a passage therebetween, means for supplying coating liquidunder pressure to said first chamber, means forming an annular valveseat around an end of said passage communicating with said irst chamber,an annular control valve adapted to seat on said valve seat to close andto open said passage to the ow of the coating liquid from said firstchamber to said second chamber, said control valve having a stemprojecting into and located wholly within said first chamber, apressure-balanced, trigger-actuated mechanism carried by said body,having means operatively engaging opposite sides of said stem, andmovable in a direction laterally of said stem to move said sternlaterally to cause said valve to rock about a point on its peripherythereby to open said valve, trigger means located outside said irstchamber and associated with said spray gun body for manually operatingsaid mechanism, means forming a spray nozzle in communication with saidsccond chamber, and a pressure-responsive discharge valve between saidsecond chamber and said spray nozzle and adapted to open rapidly whenpressure in said second chamber exceeds a predetermined value, wherebysaid coating liquid will be substantially instantaneuosly sprayed fromsaid spray nozzle when said control valve is opened.

4. A spray gun for the airless spraying of liquid coating materials,said spray gun comprising a gun body having first and second liquidchambers and a passage therbetween, means for supplying coating liquidunder pressure to said iirst chamber, a control valve associated withsaid passage to close and to open said passage to the ow of coatingliquid from said iirst chamber to said second chamber, said controlvalve having a stem projecting into and located wholly within said firstchamber, a pressure-balanced, trigger-actuated mechanism carried by saidbody and operatively connected to said stem and movable in a directionlaterally of said stem to move said stem laterally and to cause saidvalve to rock about a point on its periphery thereby to open said valve,trigger means located outside said first chamber and associated withsaid spray gun body for manually operating said mechanism, means forminga spray nozzle in communication with said second chamber, a dischargevalve located between said second chamber and said spray nozzle andnormally closing said second chamber from said spray nozzle, anoperating rod connected to said discharge valve, said ro-d having oneend subjected to atomspheric pressure and the other end connected tosaid discharge valve, a portion of the valve end of said operating rodbeing subjected to liquid pressure in said second chamber to urge saiddischarge valve toward an open position, and means associated with saidoperating rod for urging said discharge valve to a closed position,whereby said discharge valve will be opened when pressure of coatingliquid in said second chamber is built up to a point at which the forceof the coating liquid on said operating rod exceeds the force of saidurging means.

References Cited in the iile of this patent UNITED STATES PATENTS 36,238Shaw Aug. 19, 1862 1,722,985 Kling July 30, 1929 1,782,238 Kirchhan Nov.18, 1930 1,865,390 Ballard June 28, 1932 2,552,033 Bradbury May 8, 19512,626,186 Nakken Jan. 20, 1953 2,719,533 Smith Oct. 4, 1955

